Parts Geek - For 1965-1966 GMC I2500 Thermostat 15915BH. 1966 GMC I2500 4.1L 6 Cyl. 1965 GMC I2500 3.8L 6 Cyl. Notes: Fail-Safe -- The patented Fail-Safe (R) thermostat is the only thermostat on the market designed to lock in the open position, allowing coolant to continue to flow in the event of overheating.; Temperature 180F; Alternate Temp.
